Heisenberg

in reference to German physicist Werner Heisenberg (1901-1976), pioneer of quantum mechanics. His "uncertainty principle" (deduced in 1927) is that an electron may have a determinate position, or a determinate velocity, but not both.

(hī'zən-bûrg') German physicist who founded the field of quantum mechanics in 1925 and elaborated the uncertainty principle in 1927. He was awarded the Nobel Prize for physics in 1932.

Our Living Language: Philosophical problems concerning what it means to know something about the world have always been of interest to many scientists, but philosophy underwent an unexpected twist with the advent of what we now call the uncertainty principle or the Heisenberg uncertainty principle, after its discoverer. A brilliant physicist, Werner Heisenberg had made discoveries by the age os 24 that would garner him a Nobel Prize a few years later (in 1932), namely, a way of formulating quantum mechanics using the then-new branch of mathematics called matrix algebra. In 1927, he formulated a quantum mechanical indeterminacy or uncertainty principle, which concerns how accurately certain properties of subatomic particles can be measured. Earlier physical theories had held that the accuracy of such measurements was limited only by the accuracy of available instruments. Heisenberg overturned this notion by demonstrating that no matter how accurate the instruments, the quantum mechanical nature of the universe itself prevents us from having complete knowledge of every measurable property of a physical system simultaneously. For example, the more precise our knowledge of a subatomic particle's position, the less precise our knowledge of its momentum; more profoundly, the particle does not merely have a momentum that we simply cannot accurately measure, but literally does not have a determinate momentum. This principle had profound implications not just for physics, but also for twentieth-century philosophy, as it threw into question certain basic principles such as causality and determinacy, and suggested that the very act of observing the universe profoundly shapes it. Nonetheless, Heisenberg's quantum mechanical equations have led to physical theories with vast practical applications, bringing us everything from the transistor to new drugs.